Having trouble adding brick texture
First you haven't assigned your material to your walls, so, in Edit mode, select the walls, then select your brick material in the material list, and click Assign.



Now you still can't see bricks because your current material is not good.



You've plugged your Brick Texture node in the Factor of a Mix Shader, it could work like that but:

It's not the colors that will be taken into account in the Factor of your Mix Shader socket but the values, the more your color will be white the more it will let the bottom node of your mixed nodes prevail, that's why in general we plug only black, white and grey values in this socket. In your case your values are too close, so maybe only use black and white to make it clear and simple.

Beside that, in your Mix Shader sockets, you've plugged 2 Principled BSDF node that have pretty close Base Colors, so it won't allow you to see any brick precisely, maybe choose more distinct reds.

At the end it could give something like that: